The invention relates to a fuel injection system for an air-compression internal-combustion engine with electronic regulation having a signal processing unit to which signals of an accelerator pedal position sensor are fed, and a controller to adjust the position of a final control element of an injection pump. A simple regulator is connected permanently to the accelerator pedal and a switchover element which switches control of the final control element to the simple regulator.
Fully electronic regulation systems, which are known for regulating internal-combustion engines, particularly for motor cars, allow universal programmability and a large number of possible functions. However, these functions either cannot be realized, or can be realized only incompletely or through great expense, with the existing mechanical, pneumatic or hydraulic systems.
It is considered a disadvantage of the fully electronic regulation systems that, in the case of a failure of one or more electronic components, the connection between the accelerator pedal and the final control element on the engine which determines the torque is disturbed. Safety and emergency driving devices which are superimposed on the electronic regulation system to remedy this disadvantage are known. For example, emergency driving operation is possible by a control device shown in German Unexamined Published Patent Application No. 3,235,345. In that device, in the case of a failure of the regulation path sensor, the driver is able to exert an influence upon the power output of the internal-combustion engine. Due to the selector switches included in this system downstream of the signal processing unit and of the control regulator, when there is a fault, a modified signal line is formed. The signal processing unit is replaced as the connecting member between the accelerator pedal position sensor and control regulator, by a periodic voltage transformer. It is also possible to include a proportional regulator in the signal path instead of the control regulator.
It is an objective of the present invention to provide an electronically regulated fuel injection system with a switchable safety and emergency driving device, which by simple switchover, ensures a connection independent of the electronic system between the accelerator pedal and the final control element on the injection pump which determines the quantity of fuel when a fault condition exists in the electronic regulation.
This and other objects are achieved in the present invention by providing in an electronically regulated fuel injection system with a switchable safety and emergency driving device, a mechanical coupling which mechanically couples the accelerator pedal to the regulator. The mechanical coupling operatively interferes with a mechanical connection, between the controller and a final control element which determines the quantity of fuel to be injected, after a fault signal is outputted by a signal processing unit to the switchover element.
An advantage provided by the present invention is that after a fault signal from the signal processing unit of the fully electronic fuel injection system, or when there is a voltage drop for other reasons, a switchover element brings the mechanically simple regulator into engagement. Due to the construction of the kinematics, the position of the electrical controller no longer has any influence on the final control element of the injection pump which determines the fuel quantity. The switchover is designed so that whichever system is not switched in to influence the final control element continues to run idly, so as not to influence the switched-in system. A regulator which is intended solely for emergency operation driving service, with a no-load characteristic, but without special measures to stabilize the no-load characteristic, and a simplified full-load characteristic (only with final downward regulation) is used as a simple regulator.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.